August is peak season
August (and July) being peak season you won't find too many bargains.
It looks like Aer Lingus are charging 318 each way which does perhaps look a little on the steep side even for August when booking this far out
I would shop around ... going indirectly you'll might be able to save a bit ... but you're not going to find any super bargains in August really - I would be surprised if you found anything under €600 total
Most useful saving strategy would be to consider postponing to September ... that would save you a bit for sure.l